1. Field of the Invention
The present invention relates to sealing gaskets for mechanical pipe couplings of the type which generally utilize a pair of coupling segments having mated bolt pads in which the gasket is seated and engages the spaced apart juxtaposed ends of a pair of pipes intended to be joined by the mechanical coupling. Mechanical pipe couplings take numerous forms including either grooved end pipes or smooth end pipes which may or may not be flared. The couplings are exemplary and the present invention is contemplated for use wherever gaskets are useful.
2. Description of the Related Art
Pipe couplings incorporating an elastomeric gasket for use in creating and forming a sealed joint between various types of pipes, whether metal or non-metallic, generally include multi-part coupling segments or pipes and fittings or valves, often a pair of coupling segments including mated bolt pads. The segments are bolted together and in the process of joining the coupling parts, the act of closure assists in seating the gasket firmly against the pipe ends. When the coupling segments are brought into juxtaposition for purposes of securement, often radially inward, peripheral and circumferential compressive forces are applied to the gasket. As a consequence the respective sealing surfaces between the gasket and the coupling segments and between the gasket and the pipe ends are intended to engage in face-to-face relation with the objective of creating a fluid tight seal.
Many of these mechanical joining applications are used in pipe systems carrying liquids at temperatures up to about 230° F. and higher, and pressures up to approximately 1000 psi. As well couplings of this type are used with fluids of all types, including toxic and volatile chemicals.
In the past it generally has been believed that gaskets intended for use with multi-part couplings and grooved pipe ends will perform more efficiently if there is a greater amount of elastomeric material present to fill the space between the coupling segments and the pipe. However, although counterintuitive as taught herein, too great an amount of elastomeric material has been found to reduce the effectiveness of the seal between the surfaces of the gasket and the respective coupling segments and pipe surfaces. For example, in grooved pipe connections the gasket prior to its emplacement, although of one piece, has traditionally included sections of differing shapes including an annular ring shaped base which seats into the coupling segment, a pair of downwardly extending legs which nest along the inner sidewalls of the coupling and a pair of relatively wide inwardly extending lips which extend essentially to the ends of the two pipes being coupled. Generally, the upper surface of each lip was connected to the inner wall of the leg portions to form an arcuate surface with each leg. This thickened portion of the lip was considered to be highly desirable. In these prior art devices, when the coupling segments are brought together the distance between the leg and lip is reduced and the leg and lip joining area is reduced in size.
With such arrangements it has often been found that under extremely high temperatures the elastomeric material tends to swell or bulge along its inner curved surfaces and become fused. Generally elastomeric materials used with gaskets include natural and synthetic rubbers and combinations thereof and expansion of the elastomer generally exceeds expansion of the pipe by a significant factor often up to 15-20 times. In particular, with elastomeric materials such as ethylene polypropylene diene monomer (i.e. “EPDM”) fusion of the various components of the gasket under high temperatures is common, and with the result that certain critical sealing areas are left without an effective amount of sealing material.
Moreover, even in the absence of temperatures and pressures sufficient to fuse the gasket material, the distal portions of the inwardly extending lips have been found to exert relatively low pressure against the pipe surface, and often lift upwardly and become fused to the downwardly bulging leg and inner lip portion. In this condition the sealing pressures also often become significantly reduced.
Examples of these and like prior art include commonly assigned U.S. Pat. No. 1,704,003 to Johnson which relates to a pipe joint which incorporates a gasket in the form of a unitary flexible sealing ring spanning the gap between pipes intended for connection. As well, commonly assigned U.S. Pat. No. 1,808,262 to Hele-Shaw discloses a pipe joint comprising a ring of flexible material having inturned flanges adapted to embrace the pipe ends.
U.S. Pat. No. 1,867,891 to Reynolds discloses a pipe joint utilizing elastic material to contain fluid under pressure and the type of prior art sealing gaskets suggested as being appropriate to systems of this type.
Although numerous prior patents have suggested modifications to the shape of the gasket including those used for high pressure services, all have generally included a leg and lip connection area intended for close juxtaposition upon loading of the gasket and/or relatively long inwardly extending lips.
Commonly assigned U.S. Pat. No. 1,899,695 to Johnson discloses a pipe joint sealing ring of flexible material having an opening which when in position in the joint is open to fluid pressure from the pipes so as to be sealed thereby; U.S. Pat. No. 1,931,922 to Damsel, et al. discloses a laminated article in the form of a packing ring which is formed of resilient material and which is coated with a non-corrosive and non-porous plastic material; U.S. Pat. No. 1,967,466 to Damsel discloses a ring for a pipe coupling having an annular cavity in its body;
U.S. Pat. No. 2,013,267 to Damsel discloses a pipe joint in which a channel-shaped packing gasket includes a split, imperforate reinforcing and protecting ring arranged in the gasket at the bottom of a channel and has sufficient rigidity to prevent the gasket from collapsing inwardly.
Commonly assigned U.S. Pat. No. 2,766,518 to Costanzo discloses a method for joining together sections of plastic pipe which includes a gasket of the internal pressure responsive type.
Commonly assigned U.S. Pat. No. 3,080,894 to Young discloses joints between pipes of different diameter and couplings and gaskets for same.
Commonly assigned U.S. Pat. No. 4,561,678 to Kunsman discloses a pipe coupling having a gasket receiving channel for reception of a double-lipped sealing gasket. The lips of the sealing gasket extend almost to the respective ends of a pair of grooved pipes intended for joinder by the coupling.
Commonly assigned U.S. Pat. No. 4,893,843 to DeRaymond discloses a lubricant-free elastomeric gasket which is structured so as to be positioned over an intended pipe without frictional engagement with the pipe.
Other art relating to pipe couplings of various types includes commonly assigned U.S. Pat. No. 4,702,499 to DeRaymond, et al. which relates to hingeable segmented pipe couplings.
Commonly assigned U.S. Pat. No. 5,758,907 to Dole, et al. relates to a pipe coupling having mis-adjustment limiting segments with stop members at their respective ends which prevent misalignment of the coupling segments during their assembly onto the adjacent ends of pipes for fittings. This coupling includes a sealing gasket which is placed in sealing engagement with adjacent ends of the pipes to be joined.
The present invention is directed to gaskets which provide substantially improved seals between the respective sealing surfaces and the coupling components and pipes while avoiding the use of excessive elastomeric material which interferes with the desirable operation of other portions of the gasket when under the influence of compressive forces. By providing supportive gasket sealing lips which resist upward curvature, and flanges which substantially retain their basic configuration under load, and by configuring the gasket to more closely seat between the pipe ends and the assembled coupling, improved sealing can be accomplished, and fusing or other undesirable interaction will be reduced or eliminated.
Although the gaskets disclosed are illustrated as being used with pipe couplings which are adapted to join grooved pipes, the gaskets are also applicable for use in mechanical pipe couplings generally, including non-grooved pipe ends.